The applicant of the present application has proposed an apparatus for incinerating waste materials such as waste tires as disclosed in Japanese Laid-Open Patent Publication No. 2-135280. With the disclosed apparatus, a waste material is placed in a gasification furnace having a water jacket for preventing overheating, and a portion of the waste material is burned while the remainder of the waste material is subjected to dry distillation with the heat of combustion. A combustible gas produced by the gasification furnace is introduced into a combustion furnace outside the gasification furnace, in which the combustible gas is burned. The temperature in the combustion furnace is detected and the amount of oxygen supplied to the gasification furnace (specifically, oxygen required for partial combustion of the waste material) is adjusted depending on a change in the detected temperature, for thereby maintaining the temperature in the combustion furnace substantially at a predetermined temperature level. The predetermined temperature level is a temperature for causing the combustible gas to burn of its own accord, and is about 1000° C., for example. With the disclosed apparatus, the amount of oxygen required to burn the combustible gas in the combustion furnace is adjusted depending the detected temperature in the combustion furnace, so that the amount of oxygen commensurate with the amount of the combustible gas introduced into the combustion furnace is supplied to the combustion furnace to combust the combustible gas well in the combustion furnace.
The apparatus thus arranged is capable of incinerating the waste material while suppressing the emission of harmful gases into the atmosphere. Furthermore, since the combustible gas is combusted in the combustion furnace at a substantially constant temperature while the waste material is being subjected to dry distillation in the gasification furnace, the heat of combustion of the combustible gas can effectively be utilized as a heat source for boiler apparatus, etc.
Incineration residues of waste materials such as municipal waste, sewage sludge, industrial waste, etc., including incineration residues (which are basically ashes, but may include waste not completely ashed) that are left in the gasification furnace after the dry distillation of the waste material in the gasification furnace, need to be disposed of in a certain manner. According to one general process, after incineration residues are taken out of the gasification furnace, they are solidified with concrete, asphalt, etc. and disposed of.
However, objects to be disposed of according to the above process, including combustion wastes, are large in weight and volume and are difficult to handle. Since incineration residues may contain dioxins and heavy metals, they may become a secondary pollution source depending on where they are discarded.
According to another process, incineration residues are charged into a melting furnace which is held at a high temperature (e.g., a high temperature of 1400° C. or higher) and melted therein, and the melted incineration residues are cooled into a solid material.
When incineration residues are thus processed, dioxins contained therein can be decomposed, and the solid material can effectively be used as a material of the aggregate for building and construction use.
According to the above other process, however, because the melting furnace for melting incineration residues and an apparatus for heating the melting furnace are required separately from the gasification furnace and the combustion furnace, the overall equipment of the system for processing waste materials is large in size, and the cost required to introduce and maintain the equipment is high.